In mobile networks, e.g., according to the 3GPP (3rd Generation Partnership Project), it is known to use relaying for improving capacity and/or coverage of the network. For example, in 3GPP LTE (Long Term Evolution) relaying was introduced in the Release 10 Technical Specifications (TSs). The general idea of relaying is that a relay node (RN) receives a transmission from a sender and forwards this transmission to a recipient. For example, a transmission can be received from a base station, in 3GPP LTE referred to as “evolved NodeB” (eNB), and be forwarded to a mobile terminal or other type of user equipment (UE), or vice versa. In 3GPP LTE, a RN communicates with its serving eNB, also referred to as donor eNB, via a backhaul link, and provides access to the UEs attached to a relay cell of the RN via an access link. Both the backhaul link and the access link are implemented using the LTE radio interface.
According to the 3GPP TSs, a Decode and Forward (DF) type relaying operation is used to relay unicast transmissions. In this type of relaying operation, the useful signal of the sender is decoded by the RN before being forwarded to the receiver. There are basically two different realizations of RNs. There are RNs, which can separate access and backhaul links sufficiently well, e.g., by means of separated antennas, also known as Type 1b RNs, or by means of separated frequency bands, also known as Type 1a RNs. Further, there are RNs, whose access and backhaul links could interfere with each other severely such that configuration of separate access and backhaul subframes is used, also known as Type 1 RNs. In backhaul subframes, the RN can communicate with the donor eNB and in access subframes it can communicate with UEs attached to the relay cell. As defined in 3GPP TS 36.216, the RN declares downlink (DL) backhaul subframes as MBSFN (Multimedia Broadcast/Multicast Services over Single Frequency Network) subframes towards the connected UEs in order not to confuse the connected UEs during backhaul subframes.
In 3GPP LTE, Multimedia Broadcast/Multicast Services (MBMS) are provided for efficient delivery of multicast data or broadcast data. Multicast data are data intended for reception by multiple UEs, and broadcast data can be considered as a specific case of multicast data which are intended for all UEs capable of receiving the multicast data. In the context of MBMS, broadcast data may be received by all connected UEs supporting MBMS, whereas reception of multicast data may be limited to a subgroup of the connected UEs by authentication.
A MBSFN coordinates the transmission of MBMS data, i.e., broadcast data or multicast data, among a group of eNBs such that all involved eNBs jointly transmit the data, i.e., transmit the same data in a synchronized manner using the same time and frequency resources. From a UE perspective all signals combine over the air resulting in an improved signal to interference and noise ratio (SINR). MBSFN transmissions of MBMS data are carried on the Physical Multicast Channel (PMCH) and performed in the MBSFN region of the MBSFN subframe. In LTE Releases 9 and 10, the non-MBSFN region, also referred to as the control region, which consists of the first or first and second OFDM symbols, is used by the eNB to provide cell-specific control information. The size of the control region is semi-statically configured by the Multi-cell/Multicast Coordination Entity (MCE) for all cells participating in an MBSFN area and signaled via PCFICH. However, according to 3GPP TS 36.300, Section 15.1, RNs do not support MBMS.
Accordingly, there is a need for techniques which allow for efficient relaying of both unicast data and multicast data or broadcast data.